Elements having low friction pressure engagement and method of construction



May 5, 1964 c s. WHITE 3,131,978

Low RRICTTGN PRESSURE ELEMENTS HAVING ENGAGEMENT AND METHOD 0ECONSTRUCTION Original Filed Nov. l. 1956 3 Sheets-Sheet l VENTOR.

May 5, 1964 c. s. WHITE 3,131,978

ELEMENTS HAVING LOW FRICTION PRESSURE ENGAGEMENT AND METHOD OFCONSTRUCTION Original Filed Nov. 1, 1956 3 Sheets-Sheet 2 May 5,1964 c.s. WHITE 3,131,978

ELEMENTS HAVING LOW FRICTION PRESSURE ENGAGEMENT AND METHODOFCONSTRUCTION Original Filed Nov. l, 1956 3 Sheets-Sheet 3 H aFNEKS.

i United States Patent O ELEMENTS HAVING LOW FRICTION PRES- SUREENGAGEMENT AND METHOD OF CONSTRUCTION Charles S. White, Rte. 3, Box454H, Palmdale, Calif.

Application Nov. 27, 1959, Ser. No. 855,936, which is a continuation ofapplication Ser. No. 619,782, Nov. 1, 1956. Divided and this applicationOct. 23, 1961, Ser. No. 146,842

8 Claims. (Cl. 308-238) This invention relates to engaged elementshaving low friction mated surfaces, and particularly to elements havingmated surfaces which are retained in mated relation under pressure by amaterial molded thereabout, and to the elements and the methods ofconstruction., The present application is a division of the co-pendingapplicationof Charles S. White, Serial No. 855,936, filed on November27, 1959 which is a continuation of the then copending application ofCharles S. White, Serial No. 619,782 filed November 1, 1956, nowabandoned.

In the patent to Charles S. White, No. 2,804,886 issued September 3,1957, for Low Friction Fabric Material, a complete disclosure is madelof woven Teflon threads having bondable cords secured on the back facethereof. The `Teflon material has extremely low friction characteristicsand high heat resistance but in sheet and powdered formis subjected tocold iiow. Because of the extremely low friction characteristics, it issubstantially impossible to bond the Teflon material directly to othermaterials. By weaving the bondable cords on a woven fabric of Teflon,the bondable cords can be readily secured to other materials, therebyanchoring the woven Teflon material thereto. This provides a compositematerial with a face having extremely low frictional properties. In Viewof the fact that the woven material is made from threads of Teflon, coldllow is no longer present. When the Teflon is drawn into threads, itstensile strength is twenty-live times greater than the Teflon in sheetform.

: This additional strength substantially reduces or eliminates entirelythe di'iculty heretofore experienced due to cold flow. Material may nowbe provided with a low friction surface which resists cold flow, whichwithstands 500 F. temperature, and which may be bonded or otherwisesecured to other materials.

While it is possible to produce spherical surfaces Withj in a housingand on a ball, it is practically impossible to maintain diameters whiledoing so, and as a result mated machined spherical elements could not beobtained commercially. The present method of forming a ball and socketjoint embodies the use of a thin flexible cap having a face of wovenTeonfibre material which is placed about the ball. Thereafter, a material isforced about the cap which, when hardened, forms a housing for retainingthe engaged low friction surface in operating relation to the surface ofthe ball under a predetermined pressure.

Thejpresent invention further contemplates the use of a housing and balland the coverage of Teflon material about the ball surface and theapplication of a filler material which may be resin, metal and any othermaterial which may be applied hot or cold and thereafter hardened. Whenheat is employed, the temperature should be low and the material cooledas quickly as possible so that the` temperature of the Teflon materialon the ball does not rise beyond the 500 F. limit. Thus, die-cast3,131,978 Patented May 5 1964 ICC thereof. The ball, with the Teflonmaterial thereabout, may be placed within a stamping and the spacetherewithin filled with a resin, metal and the like under pressure, tothereby form a ball joint when the material hardens. The same method maybe employed for constructing cylinder and other types of bearings, aswill be explained herein.

It is within the purview of the invention to shape the Teflon clothmaterial over any surfaces to produce an antifriction relation betweentwo elements. For example, the thread of a nut and stud may have theTeflon material applied to the thread of one of the elements and aresin, metal or like material forced about the threads of the otherelement against the Teflon cloth material which, on hardening, willproduce anantifriction thread engagement under pressure between the nutand stud, eliminating any backlash therebetween. The metal, resin orother material may be hot or cold when forcing the Teflon cloth materialagainst la polished surface of an element so long as such materialhardens thereafter. Such hardened materials retain the engagementbetween the surfaces and provide a predetermined pressure therebetween.Any flowable,` formable, hardenable material known in the art to besuitable, whether molten, in powdered' or other form,'may be employedabout the element over the y Teon cloth material. The material may fillthe cavity of an encompassing housing or may be cast within a mold ordie to produceuthe housing.

Accordingly, the main objects of the invention are: to provide lowfriction engaged bearing surfaces which are simplein construction andextremely durable; to force hardenable material about engaged hard andpliable low friction surfaces for retaining them in intimaterelationship under pressure; to cast an operable element with one ormore antifriction members having low friction characteristics casttherein; to employ a barrier between the backup material and theengaging surface of the low friction material to prevent the bleeding ofmaterial therethrough; to provide a suflicient depth of pile to theflexible low friction element so that the contraction occurring duringcooling may be taken up, thereby to control the amount of pressureengagement between the surfaces, and, in general, to provide a bearinghaving a low friction cloth material backed by a hard material which issimple in construction, which provides extremely low frictioncharacteristics in the absence of lubrication, and which is economicalof manufacture.

Other objects and features of novelty of the invention will bespecifically pointed out or will become apparent when referring, for abetter understanding of the inven- FIG. 2 is a broken plan View of astrip of material forming the low friction portion of the bearingillustrated in FIG. l;

FIG. 3 is a view of the material illustrated in FIG. 2 when constructedin tubular form;

FIG. 4 is a view Aof structure, similar to that illustrated in FIG. 3,showing another form of the invention;

FIG. 5 is a sectional view of structure which applies the hardenablematerial to the low friction material to form the bearing element;

FIG. 6 is a sectional vieW of structure, similar to that illustrated inFIG. 5, showing a further form of the invention;

FIG. 7 is a viewof the low friction fabric material applied to thepolished ball of the structure illustrated in FIG. 6;

FIG. 8 is a view of structure employed to produce the element of FIG. 7;v

FIG. 9 is a view of the element illustrated in FIG. 7 as applied to theball illustrated in FIG. 6; v

FIG. 10 is a plan View of fabric material, similar to that illustratedin-FIG. Y2, showing another form thereof;

FIG. 1l is a view of structure, similar to that illustrated in FIG. 9,with the material of FIG. 10 applied thereto;

FIG. 12 is a View of structure, similar to that illustrated in FIG. 9,showing another method of applyingL the low friction material to thesurface of the ball;

FIG. 13 is a further form of theY structure illustrated in FIG. 12, witha part in section;

FIG. 14 is a plan view of an A-frame for an automotive vehicle formedintegral With-the ball structure illustrated in FIG. 6;

FIG. r15 is a view in elevation of the structure illustrated in FIG. 14;

FIG. 16'is a view of structure, similar to that illustrated in FIG. 7,showing a further form thereof as employed in the elements of FIGS. 14and 15;

FIG. 17 is a view of structure, similar to that illustrated in FIG. 16,showing a further form thereof;

FIG. 18 is a View of structure, similarto that illustrated in FIG. 17,showing still another formrof the intrated'in FIG. 17, showing a furtherapplication of the,

method as applied to the structure of FIG. 17;

FIG. 20 is a view of structure, similar to that illustrated in FIG. 16,showing a further application of the prese/nt invention; j

FIG. 21 is a view of structure, similar to that illustrated in FIGS. 6and 20, showing' a still further application of the invention, and

FIG. 22 is a broken sectional view of structure, similar to thatillustrated in FIG. 20.

The present invention embodies the ,encompassing ,of a low frictionmaterial within a solid shell to form a low friction bearing. In anotherform an element has a low friction woven fabric held against a polishedsurface of a second element by a housing which provides pressureengagement between the surfaces of the elements. The material underpressureA is appliedabout the woven material which, When'hardened, formsa casing for enclosing the fabric material and retaining it in bearingrelationship with theelement having the polished surface. By way ofexample, several such bearing elements are illustrated. In FIG. 1, acylindrical sleeve type of :bearing is shown having an internal face oflow friction material. It is to be understood that'the face of lowfriction material may be applied to the outer surface of the strips arecut and stitched or otherwise secured together to form a sleeve Si?, asillustrated in FIG. 3. In FIG. 4, two telescopedV woven sleeve portions,one of Teiion' having bondable cords on the outer face, the other of thematerial 23, are illustrated in bonded relation to each other.

Spools 25 made of two portions 26 and 27v are aligned by a centralprojection 2S on the spool portion 26 which extends within an aperture29 in the spool portion 27. The spool portions 26 and 27 are separatedand a sleeve 3i? is then slid over the central portion of the Spool andthe spool is placedk in a cylindrical aperture 32. A succession ofspools are inserted in one end of the cavity and advanced out the otherafter the spools are retained in clamped position by the clampingmembers 33 at each end of the aperture 32. Any number of the spools maybe provided in the cavity and any number of ejector nozzles may beemployed for filling the area ofthe spools. In FIG. 5 an ejector nozzle34 is illustrated, having the material 35, which is to form the hardbacking portion of the sleeveforced therefrom under pressure produced bya piston 36. When the spool is positioned in the central part of theaperture 3?.,v as herein illustrated, tne material is forced about thespool and sleeve 36, and as tion material is applied on the inner facethereof.

Referring more specifically to FIGS. l to 5, a woven Y fabric material22 has threads of low friction material forming the bearing face andcords of bondable material on the opposite face thereof. 'A thin layer23 of woven material, which` may be of cotton orvother organic nature,or which may be glass or of resinous material of the inorganicV typechosen because of the bondable properties, the ability to withstand heator the like, depending upon the specific application, is provided with acoating of bondable'material. The bondable material may be phenolformaldehyde or any resin known in the art to be suitable which bondswith the cords on the backv of the Teflon fabric 22. Only a suicientamount of the bondable material is employedr to produce a good bond withthe cords,'and in this manner a barrier is provided for preventing thematerial forming the backing portion 24 of the sleeve orthebondingmaterial itself from penetrating into the Teflon woven` fabric ortherebeyond to destroy the low friction property of the face thereof.This material is illustrated in FIG. 2 in sheet form from which soon asthe material becomes hardened, the clamps 33 are opened, the right-handspool'is advancedtherefrom as a new spool is fed into the left-hand end.v The material 35 may be of a heated plastic which is applied under apredetermined pressure to form an exact mating surface betweenthe innerface of the sleeve 30`and` the surface of the'central portion ofthevspool. A metal may be employed as the backing material in molten orpowdered form. Suflicient of the metal will enter intoV the intersticesof the layer 23k to retain the surfaceV of the cornposite sleeve againstrotation, While the resin forms a barrier preventing the material frompassing through the low friction material. The resin material willnormally bond with the resin of the layer 23 whichwill act as a barrier,limiting the penetration thereof. It is within the purview of theinvention to employ powdered resins and metals applied under pressure toform the body portion 24 of the resulting sleeve bearingV when hardened.Where resiliency is required tol the material 24, it is within thepurview of the invention to employ a rubber or rubberlike materi for thematerial 35 to thereby provide a desired degree of resiliency to thebacking portion of the sleeve bearing.

In FIGS. 7 to 13 inclusive, a further form of the invention isillustrated, that wherein the llow friction material is applied over aball of a ball joint assembly. In FIG.`6, aball stud 40 has a polishedball 41 thereon which preferably has a rust-resisting surface which maybe produced by plating chromium thereon to retain the high polish, orwhich may be a surface of low yfriction resin material, similar to theTeflon, applied in a manner as illustrated, described and claimed in theapplication of Charles SWhite, Serial No. 583,657, filed May 9, 1956,for Metal Bearing Having Low Friction Resin Surfaces, now abandoned.When employing the rust-resisting polished surface on the ball, a sealnormally employed with such ball joint assemblies may be eliminated. Inthe present arrangement, a pair of stampings 42 and 43 form theV housingfor the ball 41, having a clearance space therebetween. A cap 44, madefrom the material similar to that illustrated in FIG. 2', is placedabout the ball ofthe stud and assembled within the. stampings. Theassembly is mounted upon an arbor'having an annular end 46 which sealstheV space between the ball andthe bottom stamping and secures thebottom edge of the material of the cap 44 to the ball. The twostampings42 and 43 are secured together, preferably as by welding, the bolt 47herein illustrated being employed for mounting purposes. A nozzle 48from an injecting device forces almaterial 49 into the clearance'spacebetween thecap 44 andhousing to fill the same under pressure. Upon thehardening of the material 49, the material of cap 44 is.

. FIG. 2 has a ange 68 thereabout.

, 5 retained in engagement with the polished surface of the ball 41under a predetermined pressure, with both surfacesV accurately mated,which pressure and mated relation are maintained throughout the life ofthe assembly due to the elimination of wear between the surface of theball 41 and that of the cap 44. The material 49 may be plastic or metalwhich may be heated and flowed about the ball or which may be a resin ormetal powder applied in cold form under pressure, which hardensthereafter. The material may have elastic properties, being rubber or aresinfmaterial having rubberlike qualities of a degree. desired,depending upon the amount of cushioning required in a particularapplication of the ball joint.

The device as illustrated in FIG. 8 is employed for producing the cap44. A sleeve has an annular recess 52 in the top face aligned with anannular projection 53 in a Clamping ring 54. The ring is supported byrods 55 which extend through apertures in a flange 56 about a plunger57, the end portions 58 of which are of semispherical shape. Springs 59about the rods 55 exert a predetermined pressure upon the ring 54. Uponthe downward movement of the plunger 57, a disk 61 of the materialillustrated in FIG. 2 is iirst clamped by the annular projection 53which forces the edge portion of the material into the recess 52. Thefurther downward movement of the plunger causes its semispherical end 58to shape the material into the cap illustrated in FIG. 7. The cap may beextended beyond the semispherical portion to have a cylindrical portion62 therebelow which is slotted at 63 to permit the bottom portion towrap around-the bottom of the ball 41. Since the outer surface of thecap 44 is of a bondable resin material, a bonding strip 64, asillustrated in FIG. 9, may be wrapped therearound and bonded thereto tohave the cap encompass the entire area of the ball.

Another way of preparing the material for securement about the ball isillustrated in FIGS. 10 and 1l wherein wires 65 are woven into the Teonmaterial 66, the wires being of a `nature to bond with the metal castabout the ball, or the wires may be disposed between the two layers 22and 23 so that the resin material of the layer 23 will be available tobondwith a resin material which encompasses the ball. In eitherarrangement, the lower part of thecap 44 has the slots 63 therein,permitting the lower portion 62 to be held around the ball by thestrength of the'wires 65 when the slotted portions are forcedthereagainst.

' In FIG. l2 another form of cap is illustrated, that wherein asemicylindrical element 67 of the material of A similar cap 69 has thearcuate top .portion cut therefrom to leave an opening 71 for the ballstud 4t). The two ilanges 63 may be secured together by stitching orother securing means as the two mating faces thereof are of theTeilon-cloth material. An encompassing member may be produced by-thearrangement illustrated in FIG. 13 wherein the semispherical cap 72 hasa cylindrical portion 7.3 extending beyond the center on which thesphere was struck. A lower cap portion 74, which has the central portionremoved therefrom to provide an opening 71 for the stud 40, is placed onthe lower end of the ball, with the cylindrical portion 73 extendedthereover. A band of resin treated cloth 75 is then heat-sealed over thejoint over the adjacent outer surfaces of the cap portions 72 and '74.Tight joints are thereby produced which assure the i sealing off of thematerial forced about the ball assembly from engaging the surface of theball 41.

Having the ball 41 encased in a cup 44 in a desirable manner, any typeof housing may be formed about the ballassembly. In FIG. 6 a singlehousing is illustrated l formed about a ball, and in FIGS. 14 and l5 anentire A-frame 77 for an automotive vehicle is shown cast in the sameoperation in which housings 78 are cast about a plurality of balls toform an assembly having the ball joints thereon. The A-frame has a rod79 on which clamps are applied for attaching the A-f'rame to the body orchassis frame, with the rod in xed relation thereto. The ends of therods are provided with balls 81 having a cap 44 thereon constructed in amanner as illustrated in FIGS. 7, 9, 1l, l2 and 13, or in any othersuitable manner. At the forward end, a stud 40 is employed with asimilar cap 44 provided on the ball 41 thereof. The rod 79 with theballs 81 thereon and the stud 40 are assembled in the mold and the metalis then injected into the molds to form the housings and the A-frameherein illustrated. The particular A-frame cast with the housings andballs thereon is shown by way of example, as it is to be understood thata casting of any size, of resin or metal, having any number of balljoints or bearings thereon, may be made in a single operation in thesame manner. The A-frame is shown having a coil spring or air suspensionbag 82 secured thereon in a conventional manner. The A-frame isstrengthened by cylindrical portions 33, ribs 84 and the spring pad 85.

When heated material is employed to cast the housing 78 around the ball,various degrees of shrinkage will occur depending upon the type of resinor metal employed. For normal resins, the thickness of the two-plymaterial of FIG. 2 will provide sucient resiliency to produce thedesired pressure While absorbing the small amount of pressure due toshrinkage which may occur. When metal is employed, the shrinkage may besubstantial and result in too much pressure between the low frictionsurfaces.

In FIG. 16 a cap 44 is illustrated having a layer 86 of a cloth or otherpliable material having only the face thereof bonded to the material ofthe layer 23 from which the cap is formed. This additional thickness ofmaterial will absorb the shrinkage, and in this manner the amount ofpressure between the surface of the ball and the cap 44 will becontrolled.4 It is to be understood that the layer 23 of the capmaterial prevents any bleeding of the backup material therethrough andthrough the interstices of the threads of the Teon cloth.

In FIG. 17 a further form of` cap is illustrated, that wherein a pieceof woven Teflon cloth 87 is placed about the ball and a layer of metal88 sprayed or otherwise applied to the surface in a manner to have amechanical bond occur by the projection of the metal part way into theinterstices between the threads of the cloth. Further, in this View, acoating of chromium 89 or other rustproof material, which may be resinor other metal, is applied to the surface of the ball for the purpose ofrustprooring and providing a high polish thereto. When so rustproofed,the seals normally employed to prevent moisture, dirt and grime fromreaching the mating surfaces are eliminated. Since the surfaces areaccurately mated, non@ of the dust, dirt, grime and moisture can collecttherebetween and perfect low friction mated surfaces are providedwithout the necessity of providing a bulky seal which adds cost to thejoint and requires additional room therefor. It is to be understood thatinstead of the sprayed metal a mechanical bond may be obtained with aresin or other material or Teflon alone.

In FIG. 18 a sheet 91, embodying a layer of Teon, is' illustrated havinga layer 92 of metal, resin or other material applied thereto by a spraynozzle 93. The material will penetrate a small distance into theinterstices of the woven material and will retain the threads in fixedposisleeve 9S. The Teilon cloth material backed by the spray materialmay be employed to form caps, liners or bearings, and the like, and hasthe advantage of providing a barrier surface layer, one which bonds to abacking material of resin when the sprayed material is a resin, or whichmay bond with a backing metal when metal is sprayed on the sleeve.

In `FIG. a further application of the low friction material isillustrated, that wherein'the mated threads 97 of a shaft 9S and threads99 of a nut 161 have complete surface engagement between the lowfriction surfaces. A sleeve MP2 of the material illustrated in FIG. 2,may be performed into the shape of the thread 97 and screwed thereon, orthe sleeve may be made in two halves and pressed intothe shape of thethreads andl the two halves applied about the thread 97 and sealed atthe abutting edges with a strip of resin material. A loose sleeve of thematerial may be slid over the thread Vand forced thereabout by thebacking material when forced within the nut. When the material 1% isplaced upon the thread 97, the nut 101 is screwed thereover if thethread 99 of the nut is of such diameter as to interfere with the thread97 to prevent the disconnection of the threads in case the backingmaterial should shear or otherwise become ineffective to maintain thesleeve material 102 in engagement with the threads @7 as illustrated inFIG. 22. Sleeves 164 and IiiS are slid upon opposite ends of the shaft9S to seal the ends of the nut 101, after which the backing material 1%is forced through openings Y107 from a cylinder 168 through apertures1th) of the nut to fill the areas between the outer surface of thesleeve 102 and the inner surface of the thread 99 of the nut. Pressureis provided by a piston 111 in the cylinder 103 to provide pressureengagement between the surfaces and to assure accurate mating relationwith all points of the threads. r1`he nut 101 is of a type employed in asteering mechanism having a rack portion 112 which engagethe steeringsector on an automotive vehicle. The material 106 may be a resin, metalor any other suitable material which hardens and retains the pressureengagement between the mating thread surfaces. i

In FIG. 2l a further form of theinvention is illustrated, that wherein arod end 114 is constructed by the method herein described. A polishedball 11S which, if desired, may' have a rustproof coating thereon, has-a sleeve 116 of the material of FIG. 2 slid thereover. The sleeve maybe in cylindrical form and may be stretched to go over the ball and maynot be of sufficient elasticity to thereafter accurately engage theball. This excess material will be forced against the ball to provide acomplete area of kengagement with the ball surface. The ball and sleeveare assembled in the housing 117 on the end i of the rod 118 and afterassembly are mounted on a supporting arm 119 by a'screw 121. The end ofthe arm isflat to engage the iiat side of the housing 117, to therebyprovide a seal which prevents the escape of the backing material. Theopposite side of the housing is sealed by a truncated conical surface122 of a sleeve 123 provided on the screw 121. This truncated surfacecenters the ball within the housing so that substantially a uniformamount of the backing material 12d will be provided around the ball. Thematerial is forced from a cylinder 125 by a piston 126 through anaperture 127 in the end of the housing 117. It is to be understood thatthe arm 119 may have a similar truncated conical surface 122 to extendwithin the side of the housing 117 or that the sleeve 123 may have flatsides to engage the side of the housing, the same as the flat side ofthe arm 119. In the latter arrangement, the arm 119 will haveprojections to center the housing relative to the screw 121. Thematerial 124 may be resin or metal which may be applied hot or coldunder ypressure so long as the material hardens after filling the areabetween the ball sleeve and the inner surface of the housing. Thematerial of the sleeve 116 may be of the type herein illustrated, theTeflon cloth backed by the sprayed metal or resin, the Telion clothbonded to a fabric material, as in FIG. 2, with a further layer appliedthereto on which the metal or resin may be sprayed, or may be thematerial illustrated in FIG. 2 or a similar materialhavingwires therein,as illustrated in FlG. 10. l

All of the arrangements herein illustrated. and those not illustratedbut coming within the scope of the invention embody the formation ofbearing surfaces of the low friction type from Woven Teflon materialwhich is forced against the polished surface of an element by backingmaterial which may be resin, metal and the like which is bonded oranchored thereto in a manner to provide a barrer which prevents thebacking material from engaging the polished surface with which theTeiion material engages'. The materialis applied under pressure so thata pressure engagement is maintained between the surfaces. When thebacking material shrinks to any substantial amount, a take-up materialmay be provided on the back of the low friction element to prevent toomuch pressure from being maintained. It is to be understood that whenTefion is mentioned herein, any other low friction materials similar toTeflon, those of the liuorocarbon series and the like, known to besuitable, may be ernployed. The bearing surface thus provided requiresno lubricant and no seal since positive contact occurs at all pointsbetween the surfaces. The present invention provides a positive, cheap,substantially indestructible bearing relation by the use of the lowfriction woven cloth 'raving many applications, only a few of which havebeen herein illustrated and described by way of example.

What is claimed is:

l. A cylindrical bushing made of a fabric material having low frictionfibers on the inner surface thereof, a relatively thin hardened barrierlayer of impervious resin material secured to and covering the outersurface of said fabric material, and a hardened resin bushing materialencircling and secured k,to said impervious barrier layer, the endportionspof said fabric material and the resin bushing material backingthe end portions being flared outwardly to provide a low frictionsurface for guiding a shaft into the bushing with substantially no freefiber ends extending inwardly of the wall at the ends of the bushingaperture.

2. A cylindrical bushing comprising a sleeve of hardened resin material,the internal wall of the bore of said sleeve being flared outwardly ateach end thereof to provide rounded corners, anda layer of low frictionfabric material secured to the internal wall of said sleeve includingthe outwardly ared end portions thereof, said fabric material providinga low friction bearing surface for the bushing and the outwardly flaredportion of the fabric material at the ends of the bushing being retainedby said bushing material to Vprevent any free ends thereof being engagedby a shaft when inserted into the bushing.

3. Abushing having an internally threaded surface comprising a sleeve ofhardened resin material, the internal wall of said sleeve having aspiral thread thereon of a form smaller than that required to becompatible with 4a mating thread of the same lead, and a layer of lowfriction fabric material secured to the threads and forming a lowfriction surface thereon which is compatible with the surface of amating thread.

4. The combinationwith a shaft having a helical thread thereon, a nuthaving anfaperture containing a helical thread, said threads being inmating position to prevent endwise separation without rotation but inspaced relation due to the relative widths of the threads and groovestherebetween, a hardened low friction material filling the space betweenthe threads and grooves having one face slidably engaging one of saidthreads and the other face secured to the kother thread.

5. A cylindrical element containing a peripheral thread, a nut having anaperture containing a thread disposed on the thread of said element, thethreads being so di. mensioned as to have a space therebetween butinterrelated diametrically `to prevent endwise separation withoutrotation, a hard layer of low friction material having its front faceengaging one of the threads in slidable surface engagement therewith,and a backing material secured to said other thread and to the rear faceof said low friction layer when filling the space therebetween.

6. A cylindrical element containing a peripheral thread, a nut having anaperture containing a thread disposed on theV thread of said element,the threads being so dimensioned as to have a space therebetween butinterrelated diametrically to prevent endwise separation withoutrotation, a hard layer of low friction material having its front faceengaging one of the threads in slidable surface engagement therewith,and a backing material secured to said other thread and to the rear faceof said low friction layer when filling the space therebetween, at leasta portion of the material of said layer being tetrauoroethylene resin.

7. In a steering mechanism, a housing, a shaft journaled in said housinghaving a helical thread thereon, a

traveling nut having an aperture containing a helical thread, saidthreads being in mating position to prevent endwise separation withoutrotation but in spaced relation due to the relative widths of thethreads and grooves, a hard low friction layer having one face engagingone of said threads, and a backing material engaging the other face ofsaid layer and secured thereto and to said other thread and filling thespace therebetween, at least a portion of the material of said layerbeing tetrauoroethylene resin.

8. A cylindrical element containing a peripheral thread, a nut having anaperture containing a thread disposed on the thread of said element, thethreads being so dimensioned as to have a space therebetween butinterrelated diainetricaily to prevent endwise separation withoutrotation, a hard layer of low friction cloth-like material having itsfront face engaging one of the threads in surface engagement therewith,and a backing material secured to said other thread and to the rear faceof said low friction layer when filling the space therebetween.

References Cited in the file of this patent UNITED STATES PATENTS2,219,054 Palm Oct. 22, 1940 2,276,143 Bell Mar. l0, 1942 2,580,438Knoblaugh Ian. l, 1952 2,691,814 Tait Oct. 19, 1954

1. A CYLINDRICAL BUSHING MADE OF A FABRIC MATERIAL HAVING LOW FRICTIONFIBERS ON THE INNER SURFACE THEREOF, A RELATIVELY THIN HARDENED BARRIERLAYER OF IMPERVIOUS RESIN MATERIAL SECURED TO AND COVERING THE OUTERSURFACE OF SAID FABRIC MATERIAL, AND A HARDENED RESIN BUSHING MATERIALENCIRCLING AND SECURED TO SAID IMPERVIOUS BARRIER LAYER, THE ENDPORTIONS OF SAID FABRIC MATERIAL AND THE RESIN BUSHING MATERIAL BACKINGTHE END PORTIONS BEING FLARED OUTWARDLY TO PROVIDE A LOW FRICTIONSURFACE FOR GUIDING A SHAFT INTO THE BUSHING WITH SUBSTANTIALLY NO FREEFIBER ENDS EXTENDING INWARDLY OF THE WALL AT THE ENDS OF THE BUSHINGAPERTURE.